The mass shooter, who took his own life, sprayed gunfire down on the helpless and panicked crowd of 22,000 for five terrifying minutes from a perch in the Mandalay Bay Hotel and Casino, according to one witness.

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The Sin City carnage became the deadliest mass shooting in modern U.S. history, eclipsing the 2016 killing spree that left 49 dead at the Pulse nightclub in Orlando, Fla.

"It was an act of pure evil," declared President Trump, who plans a Wednesday visit to Las Vegas.

Country music fans scrambled for their lives beneath the massive Vegas hotel as Jason Aldean performed on the last evening of the three-night Route 91 Harvest Festival.

Killer Stephen Paddock unleashed his unrelenting attack at 10:08 p.m. as the night of music ended suddenly to a soundtrack of automatic weapon fire.

People run from the Route 91 Harvest country music festival after gun fire rang out, killing 59 people and injuring about 515. (David Becker/Getty Images)

"Panic ensued," survivor Joseph Ortunio told CNN on Monday afternoon. "It was like a war zone. People were just dropping to the ground and running."

Ortunio said he and a friend who took a bullet to the shoulder scaled a 10-foot fence to escape the gunfire. The wounded woman was expected to recover, he said.

Paddock had converted his hotel room into a lethal armory, smuggling 18 to 20 guns and hundreds of rounds of ammunition inside after checking in last Thursday, authorities said.

An analysis of the shooting video showed Paddock fired a staggering 280 rounds in one 31-second span.

Mass shooting at Mandalay Bay Hotel and Casino in Las Vegas

Mike McGarry, a Philadelphia financial advisor at the show, wore a shirt with footprints on its back after he was trampled by people bolting from the outdoor venue.

Authorities warned the numbers of dead and wounded were likely to rise as the day went forward.

The sound of weapon fire rang out as Aldean stood singing at the microphone. Both the music and the shooting came to a brief halt before Paddock started opened fire a second time.

"It was the craziest stuff I've ever seen in my entire life," said concert survivor Kodiak Yazzie, 36. "You could hear the noise was coming from west of us, from Mandalay Bay. You could see a flash-flash-flash (of muzzle fire)."

Federal authorities provided no immediate motive for the Mesquite, Nev., man's rampage, but shot down an ISIS spokesman's claim that Paddock was one of the terror group's "soldiers."

Blown out windows can be seen on the 32nd floor of the Mandalay Bay Resort and Casino after Stephen Paddock opened fire on a Las Vegas music festival. (David Becker/Getty Images)

"We have determined to this point no connection to an international terrorist group," said FBI Special Agent Aaron Rouse of the Las Vegas office.

ISIS responded with a second communique that identified the typically apolitical Paddock as "Abu Abdul Barr al-Amriki," describing him as a martyr for the Islamic cause.

Paddock likely acted alone, according to Clark County Sheriff Joe Lombardo. After searching the sprawling hotel floor-by-floor, police blasted open the door to Paddock's room and found him dead.

Reports indicated that smoke from Paddock's furious firing set off alarms that were still ringing inside the room when law enforcement arrived.

Paddock actually rented two rooms in the hotel, making his stand in the one overlooking the concert venue more than 1,000 feet away, said Clark County Commission Chair Steve Sisolak.

Stampedes of frightened people flooded multiple streets along the Strip and a restricted area at the nearby McCarran International Airport. The panic prompted the Las Vegas airport to halt all flights for hours as police investigated the shooting.

Brooklyn poker player James (Action Jim) Boccanfuso and his pal, Ruslan Krasikov, missed the bloodshed by minutes. The New Yorkers left Mandalay Bay in an Uber for their flight to Chicago.

They encountered floods of people, some bloodied, looking for refuge at the airport. The terrified concertgoers tried opening the Uber car doors, "thinking the doors were unlocked," Krasikov said.

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"They were begging to get into the car with us," Boccanfuso told the Daily News. "Never in my life did I see people running for their lives."

"The people were scared to death," he said.

The wounded inundated five hospitals in the Las Vegas area. Half of the injured — including a dozen in critical condition — were taken to UMC Hospital.

Police radio transmissions revealed a chaotic, confusing scene, with SWAT officers closing in on the suspect and other police units scrambling to nearby hotels to determine if multiple reports of additional shootings were real. There has no evidence of other attackers.

MGM Resorts International said in a statement that it locked down many of its nearby hotels along the southern end of the Strip, per the advice of law enforcement.

Lombardo said authorities found two vehicles believed to be associated with the suspected shooter.